@ danger:
Well... I don't think, that in case u don't know a track (which will happen most of the time i guess) a MIDI keyboard will help you to react faster or better or more appropriate regarding the music!
You cannot be 100% music matching all the time anyway. otherwise u will have to premade musicvideos for each track the DJ is going to play.
how are you trying to go along with the music? are you trying to cut to the beat? are you adjusting the playbackspeed to the music's bpm? are you trying to match the mood the music evokes? how?
to come back to the topic again, which were MIDI controllers...
Regarding Resolume, I think that a MIDI controller is not an absolute necessity! the interface was designed to be controlled with mouse and keyboard primarily, i believe, so why not use it!
but on the other hand, finetuning all kind of layer parameters (eg. speed, opacity, effects) with a mouse is very hard, not to say impossible.
so if u are into finetuning, i would recommend some kind of controller...
the POWERMATE is indeed very usefull (not MIDI), DOEPFER controllers seem very usefull too. as i posted somewhere before, go for potis and faders! u wont need an expensive studio controller or master keyboard. the use of the piano roll in resolume is minimal, from my poit o view!
i hope, all this gossip is usefull for anyone. if not, forget it.
have a nice day,
the|randelman